In recent years, there have been reported infections of avian influenza to humans, and there are concerns about a lot of damage caused by a large epidemic (pandemic) of infections from human to human. Consequently, prepandemic vaccines which have the possibility of being effective against the avian influenza are being stockpiled all over the world. Also, in order to administer the prepandemic vaccines to many people, there have been carried out examinations for enlarging the manufacturing quantities of the vaccines.
The skin is composed of three portions: the epidermis, the dermis, and the subcutaneous tissue. The epidermis is a layer ranging between approximately 50 μm and 200 μm from the surface of the skin, and the dermis is a layer ranging between approximately 1.5 mm and 3.5 mm continuous from the epidermis. An influenza vaccine is ordinarily administered in a hypodermic or intramuscular manner, and therefore, it is injected into a lower layer portion of the skin or a portion deeper than the lower layer portion.
On the other hand, there was reported an article that an immune obtaining response equivalent to a hypodemic administration and a muscle administration can be obtained by administering influenza vaccine in a situation of making an upper layer region of a skin where a lot of immunocompetent cells exist as a target region even if the applied dose is reduced. Therefore, it is possible to reduce the applied dose by administering the avian influenza vaccine into the upper layer region of the skin, so that there is a possibility that the avian influenza vaccine can be administered to more people. Note that the wording “upper layer region of the skin” indicates “epidermis” and “dermis” within the skin.
As administration methods of medicine to an upper layer region of a skin, there have been reported methods using a single needle, multiple needles, a patch, gas and the like. Then, when taking stability, reliability and manufacturing cost of the administration into account, the method using a single needle is the most suitable as the administration method to the upper layer region of the skin. As this method of administering vaccine to an upper layer region of a skin by using a single needle, there has been known a Mantoux method from old times. The Mantoux method is a method in which medicine of around 100 μL is administered by inserting a needle having a needle tip of short bevel with a size of generally 26 to 27 gauge by an amount of around 2 mm to 5 mm from an oblique direction of around 10° to 15° with respect to the skin.
However, in the Mantoux method, the procedure thereof is difficult, and the procedure is left up to the skill of a doctor who carries out the injection. In particular, there is a possibility that the infant may move at the time of administration, so that it is difficult to administer influenza vaccine by the Mantoux method. Therefore, development of a device is required which can easily administer vaccine to the upper layer region of the skin.
In Patent Document 1, there is described an injection apparatus in which a limiter having a skin contact surface is connected to a needle hub of an injector. The limiter of the injection apparatus described in this Patent Document 1 is formed in a tubular shape covering the periphery of the needle tube and includes a skin contact surface from which the injection needle protrudes. This limiter restricts the length of the injection needle (protrusion length) protruding from the skin contact surface to the range of 0.5 mm to 3.0 mm and the medicine injected from the injection needle is made to be administered into the inside of the skin.
Also, In Patent Document 2, there is described an apparatus relating to a sticking adjuster for an injection needle and an injection needle assembly provided with that adjuster which prevent the injection needle from being stuck more deeply than an aimed depth. Within the sticking adjusters for injection needles disclosed in this Patent Document 2, there exists a sticking adjuster for an injection needle which closely-contacts with the periphery of the injection needle and which includes a skin contact surface.